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Investment Securities (Significant Unobservable Inputs) (Details) - NR - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2018 | Dec. 31, 2017
Private equity security |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Time until expiration of security | 4 years | 4 years
Volatility rate | 50.00% | 50.00%
Risk free rate | 1.77% | 1.77%
Private equity security | Recent transaction |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure | $ 15.8 |
Valuation technique | 338.85 |
Private equity security | Option pricing method |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure |  | $ 11.3
Valuation technique |  | 0.21
Private debt instrument | Discounted cash flows |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure | $ 10.5 |
Valuation technique | 0.0962 |
Convertible Preferred Stock | Discounted cash flows |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure | $ 14.5 | $ 14.5
Valuation technique | .30 | .30
Convertible Preferred Stock | Multiple of EBITDA |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure | $ 3.5 | $ 0.6
Valuation technique | 6 | 6
Investment B | Private equity security | Discounted cash flows |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure | $ 21.0 | $ 21.0
Valuation technique | 0.25 | 0.25
Investment E | Private equity security | Discounted cash flows |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure | $ 22.1 | $ 22.1
Valuation technique | 0.35 | 0.35
Investment C | Private equity security | Recent transaction |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure | $ 28.3 |
Valuation technique | 56.60 |
Investment A | Private equity security | Recent transaction |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |
Assets, Fair Value Disclosure |  | $ 3.6
Valuation technique |  | 2.521

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